Bluetooth® is a short-range, open wireless communications standard that includes different transmission modes and can simultaneously accommodate different types of devices. Bluetooth is often referred to as a PAN (Personal Area Network) and has the ability to carry real time voice data via a SCO (Synchronous Connection Oriented) link. An SCO link is a digital transmission mode where voice packets transmitted back and forth between an audio gateway (e.g. a mobile cellular phone) and a headset are sent based on a clock common to both devices. Packets that are not received by one of either the headset or audio gateway are not retransmitted. The Bluetooth specification in its entirety is available for download at www.bluetooth.org. Key specification documents include the Bluetooth Core Specification v1.2, Hands-free profile and Headset profile, all of which are incorporated herein by reference. While the present invention is described with respect to headsets and systems utilizing the Bluetooth standard, it is not necessarily limited to this particular communications protocol.
Wireless audio gateways that utilize Bluetooth are known. Such gateways are sources of audio, such as a mobile cellular phone, that route audio transmissions from one communications system (e.g. a cellular network) to another communications system (e.g. a Bluetooth wireless transmission system). A wireless transmission system can include a wireless headset, which is a wearable audio communication device that includes a wireless transceiver, a microphone, a speaker (often called a receiver) and a battery. The headset can both receive an audio transmission and play the transmission for the wearer, as well as send the wearer's voice as an audio transmission. A typical headset includes controls for answering and ending calls, for adjusting the volume of the audio, and for turning the headset on and off. Recently, more models of mobile cellular phones are including the gateway feature.
Wireless headsets using the Bluetooth communications protocol allow users to conveniently communicate via their mobile phone without the constraint of a wire running from the headset to the phone. Use of a wireless headset eliminates the tangling of wires that is so common with wired headsets. Wireless headsets afford new conveniences, such as allowing a user to leave their phone in their pocket, briefcase, or purse. When the phone rings, the user can quickly don the headset and answer the call by activating the answer button on the headset. When used in an office situation, the user of a wireless headset can roam away from their desk wearing the headset, and not have to carry their mobile phone with them. Some users choose to constantly wear the headset, which further reduces the effort required to answer a call. This function is particularly useful in the car while driving. In fact, some jurisdictions have passed laws that prohibit holding a phone while operating a motor vehicle.
Wireless automotive hands-free systems (hereafter hands-free system) are also well known. Such systems are located in automobiles and include a wireless transceiver, a microphone for picking up a user's speech, and a speaker system for playing the caller's audio transmission. Like headsets, the hands-free system includes controls for answering and ending calls, and for adjusting the volume of the audio.
Hands-free systems for use in automobiles have been developed to enable drivers to make and receive calls with minimal physical and cognitive interaction. For example, answering a phone call requires a single button activation. Hands-free systems use speakers to play the caller's voice. The drawback to hands-free systems is that there is no privacy during the call. Everyone in the car listens to the conversation. Additionally, hands-free systems can produce poor quality transmitted audio because the microphone is usually located far away from the user's mouth and the car is a noisy environment. Therefore, hands-free systems, especially aftermarket integrated systems that plug into cigarette lighters, can be particularly unpleasant to listen to at the other end of the conversation.
One problem with headsets and hands-free systems is that when the phone moves out of range of the headset or hands-free system, the connection is lost. One function that is occasionally implemented in headsets and hands-free systems is to automatically and periodically page the mobile phone to which it was last connected in an attempt to reconnect. In theory, the process works like this: a headset and phone are paired and connected. If the phone moves out of range of the headset and the connection is lost, the headset will begin to continually page (attempt to reconnect to) the phone. When the phone again comes into RF range of the headset, they automatically reconnect. Ideally, this would take only a few seconds.
In the case of when a headset is used in a car, the reconnect function in practice is not reliable. Many headsets don't implement the reconnect function because its reconnection duty-cycle requires power to page the phone, thus reducing the talk time and standby time (battery life) of the headset. Some headsets will only attempt to reconnect for a finite length of time and then stop paging the phone to conserve battery power.
Another problem with using headsets in a car is that if the wearer doesn't want to constantly wear the headset, it is easily lost or misplaced of because there is no fixed storage spot for the headset. The motions of the car may cause the headset to move around or fall between the seats. Headsets are small and not easily located, especially in a dark car.
Wireless headsets, although convenient, impose the requirement of having to be charged. A user of a wireless headset already must remember to charge their mobile phone. There are many other popular devices that user's must remember to charge, such as portable MP3 players, Personal Digital Assistants (PDAs), and gaming devices. A wireless headset is just one more item that must be carried to the charging location.
Some manufactures have attempted to make chargers that work with both mobile phones and headsets. For example, the Motorola H500 headset includes a USB-type connector that is used for charging, and thus can be charged using the same car cigarette lighter charging adapter that is used to charge Motorola mobile phones that also include the same USB connector. However, when the headset is being charged, it is inactive (meaning that it is not connectable to the phone). Furthermore, when the headset is unplugged, it doesn't automatically connect to the phone. If a call is received while the headset is charging, the user must unplug the headset and cycle power to the headset, which would take too long and the call would be missed. Since charging the headset requires plugging it into the USB connector at the end of a cable, it is a two-handed operation that requires a substantial amount of the user's attention and manual dexterity, and can be difficult for the driver of a car to accomplish while driving. Lastly, the mobile phone usually cannot be charged while the headset is charging in the car, because most cars have only one cigarette lighter.
FIG. 1 shows the Jabra model BT250 headset manufactured by GN Netcom of Denmark, in a charging dock. This dock can be used in the car in conjunction with an automotive DC-to-DC cigarette lighter adapter. However, it also takes two hands to place the Jabra BT250 into the dock, or remove the Jabra from the dock, due to the tight friction fit between the headset and the dock. Furthermore, the headset is not in a functional state while charging. If the user's phone rings, it is unlikely that the headset can be removed from the dock, powered up and connected to the mobile phone in time to answer the call.
What is needed is a wireless headset system for an automobile that provides an effective docking solution for a wireless headset that allows operation during charging and easy removal for answering calls. The system should also incorporate an improved automatic reconnection function such that the headset battery is not needlessly drained, yet is transparent to the user during use. Lastly, the system should allow for simultaneous charging of the phone and headset.